The invention relates to virulence factors of Salmonella typhimurium. 
Salmonella typhimurium (S. typhimurium) enter epithelial cells by a process termed bacterial-mediated endocytosis. S. typhimurium stimulates these normally nonphagocytic cells to undergo significant cytoskeletal rearrangements that are visualized as localized membrane ruffling adjacent to the bacteria. Bacteria are then internalized via membrane-bound vacuoles formed from the membrane ruffles.
Several S. typhimurium loci have been identified that are required for the induction of bacterial-mediated endocytosis (BME) by epithelial cells. Many of these epithelial-cell signaling loci have a similar chromosomal location, clustered within a 40 kb “virulence island” located between 59 and 60 minutes on the S. typhimurium chromosome (Mills et al., Mol. Microbiol. 15:749-759, 1995). InvJ is a S. tymphimurium gene which is thought to encode a secreted protein necessary for BME (Collazo et al., Mol. Microbiol. 15:25-38, 1995).